Monday, January 24, 2011

Adiantum reniforme, a living fossil fern

This strange fern of rounded fronds belongs to the family of Adiantaceae and  it is an antediluvian relic, a small living fossil. Its global dispersed distribution with widely separated populations that have evolved separately and have given rise to local varieties, suggests the great antiquity of Adiantum reniforme that several million years ago, in a cold period with the level of Oceans lower than currently, populate a vast region covering much of Asia, Africa, Madagascar and Macaronesia. Later, as a result of a global climate warming, the ocean water level rose and separated the Asian populations from those African and those African from those Macaronesian and Malagasy.

Adiantum reniforme in the Bosque de Los Tiles on the island of La Palma in early May. (Double click on the photo to enlarge.)

Botanists are six varieties within the species:

-Adiantum reniforme var. reniforme, growing in Madeira, the Canary Archipelago and the islands of Cape Verde;
-Adiantum reniforme var. pusillum, a dwarf variety endemic to the Canaries, who lives in all the islands except Lanzarote and Fuerteventura;
 -Adiantum reniforme var. asarifolium, a rare hairy version with thick black margins and large sori, found in Madagascar, Mauritius, Réunion, South Africa, Kenya, Malawi, Gambia and Senegal;
-Adiantum reniforme var. hydrocotyloides, exclusive of the island of Réunion;
-Adiantum reniforme var. crenatum, which lives only in Madagascar;
-Adiantum reniforme var. sinense, which grows only in China and is in serious danger of extinction, with only four small populations known in the region of the Three Gorges of the Yangtze River, between the province of Sichuan and the province of Hubei, a place regarded as a refuge of plants that survived to Quaternary glaciations. 

Group of Adiantum reniforme in the Bosque de Los Tiles with the copy of the previous picture in a very damp wall facing north. 

In the Macaronesian Islands this fern prefers to live in habitats on rupicole rocks and walls oozing bright but not direct sun in the laurel forest clearings, with a subtropical climate and frost-free. In South Africa, Madagascar, Mauritius and Reunion Island it grows in rainforests with a similar climate to Macaronesia. In Kenya, Gambia, Malawi and Senegal, have a tropical climate too warm for this fern, is confined to the mountains where the climate is cooler and more humid. The four small Chinese populations living in the Three Gorges of Yangtze River also prefer cool and moist habitats, free of frost, located between 80 and 480 meters. Given the increasing human exploitation of this region of China, the number of copies of Adiantum reniforme var. sinense is decreasing at an alarming rate and now stands at a dramatic extinction. 

Adiantum reniforme growing between the stones of a wall facing north in the town of Los Sauces in the island of La Palma. This fern is highly resistant to long periods of drought. In the picture looks like moss growing on the fern is completely dry.

Beautiful specimen of Adiantum reniforme growing on a bed of moss in the cleft of a rock oriented northeast in the Portuguese island of Madeira in mid-May. Long petioles are appreciated black or dark brown on each frond with small rounded blade on the end. (Double click on the photo to enlarge) 

Several  fronds of Adiantum reniforme with its beautiful design in the form of Chinese pai-pai. Shows the radial flabellate arrangement of nerves of blade, which usually measure between 3 and 5 inches in diameter, has a leathery texture as plastic and presents a vivid green. In the Canary Islands this fern is called " tostonera" for its resemblance to an ancient coin called "toston", which was used in Spain and the American colonies during the sixteenth century.

Underside of a frond of Adiantum reniforme with the beautiful distribution of sori in the blade edge. Particularly striking is its reniform or kidney-shaped  form that gives the species name, design radial nerves and the fine pilosity covering the underside of the blade.

Detail of sori still immature and the fine light brown pilosity covering the underside of the blade. (Double click on the photo to enlarge.)

Adiantum reniforme sori watched side with his edged pseudoindusium. When the sporangia are ripe, the pseudoindusium be lifted to allow dispersal of spores. 
Microphotograph of an sporangium of Adiantum reniforme with mature spores within the transparent bag, before being dispersed.

Adiantum reniforme spores, very large and golden brown.

Friday, January 21, 2011

It kills the Maori of New Zealand

Its beauty is deceptive and treacherous, as its innocent appearance hides fern highly carcinogenic substances, which cause various cancers in both animals and humans. I am speaking of Pteridium aquilinum, a fern of the family Hypolepidaceae widely distributed throughout the world, except Antarctica. In the genus Pteridium stands a single species: aquilinum, two subspecies: aquilinum and caudatum and twelve varieties.
Vigorous new fronds in a copy of Pteridium aquilinum on the beach in Los Cancajos of the Canary island of La Palma in May.

The Maori of New Zealand cultivated this fern for its rhizomes, from which they obtain a flour to make bread to feed it. Carcinogenic substances from the rhizomes are responsible for the high rate of gastric cancer among these natives of up to two and a half times higher than the rest of the New Zealand population.

 Pteridium aquilinum growing in the mountains at about 1000 m in the Pla de Cuber of the Serra de Tramuntana in Mallorca Island in the middle of July.               
In Venezuela and Costa Rica, where the fern grows into large pasture in the highlands, there called "potreros" cattle feed on the fronds, which are carcinogens that cause the disease called Bovine enzootic hematuria, commonly known as "orinadera de sangre", guilty of the death of a large number of cows, oxen and breeding bulls, in which causes bone marrow depression with leukopenia, thrombocytopenia and severe anemia, exacerbated by bladder tumors that bleed profusely. It also produces cancer in bladder of water buffaloes  and in the intestine and bladder of the sheep that graze on these pastures invaded by the fern, which behaves as an invasive plant and shifts the normal vegetation.

The Bovine enzootic hematuria has been observed in numerous countries as diverse as New Zealand, Brazil, Sweden, England, Canada and Fiji, although the most affected Venezuela and Costa Rica.

Humans who consume contaminated milk from cows that feed on the fronds of Pteridium aquilinum have a high rate of stomach cancer, much higher than expected in any human population. Costa Rica ranks third worldwide in incidence and mortality from stomach cancer. The carcinogenic substances found in milk are shikimic acid, quercetin, aquilide A and above all ptaquiloside, which is considered the main toxic principle and is in highest concentration in the tender fronds. Was isolated in 1983 and its carcinogenic toxicity  in laboratory animals such as rats, mice, quail, dogs, hamsters, etc. .. , in which causes malignant  neoplasm of bowel, bladder, lung and lymphatic leukemia, was shown in 1984. It was also demonstrated experimentally the toxicity in cattle. When ingested is broken down into a chemical  second derivative called dienone, which is the real toxic and cause direct damage to DNA and activation of oncogenes. 

Cows graze in pastures where it not grows Pteridium aquilinum not have the hematuric disease and their milk is free from carcinogenic pollutants, which affects the health of humans who feed on their milk, which present a very low rate gastric cancer, similar to that expected in any human population.

Grassland invaded by Pteridium aquilinum in a clearing in the Sierra de Grazalema Natural Park in the Cadiz province in mid-May.

The Pteridium aquilinum also contains large amounts of the enzyme thiaminase which destroys thiamine or vitamin B1, causing a severe vitamin deficiency similar to beriberi, with motor incoordination, paralysis and seizures, even to cause death by motor suffocation if they have consumed large amounts of fern. This issue primarily affects non ruminant animals such as pigs, horses, mules and donkeys, not affecting ruminants for the large amounts of thiamin synthesized by the ruminal flora.

Copy of Pteridium aquilinum in an oak of Natural Park of Los Alcornocales in the province of Cadiz.

In the sheep causes progressive blindness due to degeneration of the retina and cerebrocortical necrosis, dying of starvation by not being able to drink or feed or follow the herd on the move.

      Pteridium aquilinum sprouting in early May on the outskirts of the city of Horta on Faial Island in the Azores Archipelago

In Japan, where it is customary in some areas to feed on the tender fronds of Pteridium aquilinum, found a clear relationship between consumption and the incidence of cancer of the esophagus and stomach. In these regions is considered a vegetable and is called Warabi. You can see it on sale in markets. Families out for a walk in the field are used to collect the tender fronds of this fern, for cooking later in their homes.
 Pteridium aquilinum growing as an epiphyte on the trunk of a Canary date palm, Phoenix canariensis, in the city of Barlovento of La Palma Island.

In Brazil, in areas where abundant, its tender fronds are also eaten as vegetables and is studying the clear relationship between their consumption and the high incidence of stomach and esophageal cancer.

        Underside of a frond of Pteridium aquilinum with mature sori.    

Studies in Asia have noted that the tender fronds cooking at high temperatures in traditional woks neutralizes carcinogens, and can be safely consumed. Just not suitable for consumption raw or lightly cooking. However, these assertions are contradicted by the high rate of cancer of the Maori eating bread made with flour from rhizomes, logically high temperature ovens.

The sori are covered on the outside by a pseudoindusium formed by the revolute margins of the pinna and on the inside by a true indusium brown membranaceous and fimbriate edge.
Some studies also suggest that the simple inhalation of spores can cause lung cancer, but has not been demonstrated.

In Wales, western England, where it grows in abundance Pteridium aquilinum, there has been an unusual incidence of cancer among the human population. Not being consumed as food, has blamed the contamination of well water exudative fern root and the incorporation of spores into the water in surface water systems, but has not been demonstrated any relationship.

A deep-rooted custom is padded with fronds of Pteridium aquilinum boxes with fresh oysters. In this case perhaps the danger is contamination with spores of the fern open oysters and placed on the fronds.

In countries where this fern behaves as an invasive weed, crowding out the normal grass, are studying various methods of eradication, which to date have been too costly and ineffective.

And finally in the air is a question: why such toxicity?. The answer could perhaps be the same as for the tiny poison frogs of the Amazon forests: the fern Pteridium aquilinum funnels large amounts of toxic substances in their tissues simply not be eaten, to protect itself, to eliminate by a slow and cruel form its predators, ultimately, to survive and  in the light of the results, their strategy has not done anything wrong. 

Saturday, January 15, 2011

Ophioglossum lusitanicum, a small big champion

In appearance no one would say that it is a fern, since their tiny sterile fronds seem leaves of grass. Their habitat are the clears of Mediterranean scrubland whose clay soils moss-covered remain wet during the fall and winter. Their neighbors are the Cistus, several orchids, Pistacia, Asphodelus, Asparagus, rosemary, Phillyrea angustifolia, Gagea nevadensis, Crocus cambessedesii, wild olive trees, white pines, Brachypodium retusum, Plantago bellardii, Arisarum vulgare, Arum pictum, etc ...

Ophioglossum lusitanicum fall with 4 sterile fronds no more than 3 cm long and fertile fronds with immature sporangia. (Double click on the photo to enlarge) 

Its life cycle is completed in about 7 months. During the dry and hot summers of Mallorca lies dormant in aestivation underground as small rhizomes, oblong or subglobose, brown, with thick roots, sometimes stoloniferous, so that over the years may be forming a little family around him through of underground stolons, each of which sprouts a new fern clone with the first rains of autumn.

Another fine specimen with a single sterile frond and a fertile frond with a stem at its apical end, formed by two rows of sporangia, in this case is still immature. Picture taken in late November.

Detail of the fertile frond stem above with the two rows of immature sporangia. 

Ophioglossum lusitanicum Group with small leaves resembling grass, which is easily confused with other herbs with which it shares habitat. These small leaves or sterile fronds sprout from the rhizome that is rooted deeply in the clay. In the picture looks as leverage to spring the soil cracks formed during the dry summer, which was cracked by the hot sun scorched Mallorca. When fertile fronds disperse the spores, they also take advantage of these deep cracks to germinate and thus be able to withstand the 5 or 6 long months of drought.

Detailed picture of the sterile frond thick, fleshy, linear-lanceolate or oblong-lanceolate, slightly fluted, to collect the morning dew and direct moisture away from the rhizome. Is also seen clearly how a crack exploit ferns soil to sprout, which saves them considerable energy, as well as their fronds do not have to go through the thick, hard clay soil. Ophioglossum are accompanying by the long filiform leaves and V-shaped grooved a Merendera filifolia, the tiny new shoots of mosses and liverworts several hatchlings of the species Oxymitra incrassata, quite abundant in the same garrigue, like lichen Diploschistes steppicus

Each Ophioglossum lusitanicum can have from one to four sterile fronds and one or two fertile fronds, as the copy of the photo. The comparison with the tip of my index finger gives us an idea of the tiny size of the ferns. In this case the sterile fronds are less than 2 cms and fertile little over 3 inches. 

Throughout the fall are sprouting new fronds accumulating energy to produce spores. Every morning, but no rain, dew moisture received, which is absorbed by the moss, which acts like a sponge, keeping the soil constantly moist clay. In early or mid-winter, depending on how early or late in the first autumn rains, it starts the maturation of sporangia and spore dispersal.

Stem with the two rows of mature sporangia initiated in February the dispersal of spores.

Each sporangium opens like a mouth with two lips and inside out transparent spores that fall close to his mother. If you are lucky and end up at the bottom of a small crack in the ground, germinate and give rise to the gametophytes, which produce and anterozoides oosphere. Once fertilization has taken place in the oosphere, created a new Ophioglossum lusitanicum the bottom of the crack. All this may take a couple of years and depends on a symbiotic fungus, probably of the genus Glomus, that mycorrhizal rhizoids of gametophytes of Ophioglossum and facilitates the production of gametes. This is mycorrhizae with arbuscular hyphae. The new true fern or sporophytes spring from a fertilized oosphere of mycorrhized gametophyte. Without this symbiotic fungus-fern, it is not possible to reproduce the ferns of the genus Ophioglossum.

Detail of the stem of a fertile frond with mature sporangia open like mouths, inside which the spores out aided by the wind and rain.

As if they were painted lips with crimson, the two halves of each sporangium open and disperse the whitish and transparent spores.

In this picture look better microscopic spores out of the sporangia. (Double click on the picture to enlarge)

Details of Ophioglossum lusitanicum spores, which have a concavity in form of fovea on one side. The photomicrograph is made with very little light because the spores are really transparent. 

Saturday, January 8, 2011

Doodia caudata, a beautiful Australian with cosmopolitan vocation

Its new fronds of bright red and easy cultivation make it very attractive for gardeners who love the ferns. From Australia, Tasmania, New Zealand, New Caledonia and Lord Howe Island, which is called "small raspfern" has been taken by man to many other places on Earth. In countries of temperate and humid climate similar to their southern land it is grown outdoors as an ornamental. In countries of very dry or cold weather is treated as a houseplant. In nature, living on slightly acidic soils and well drained mainly shaded riparian habitats on the banks of rivers, streams and creeks. Tasmania is ranked in danger of extinction. It needs constant moisture throughout the year. It has become naturalized in the Azores and Madeira.

Beautiful Doodia caudata in cool, moist slopes towards the north of a volcanic mountain (Caldeira do Faial) in the center of the island of Faial in the Azores Archipelago. Its new fronds are very attractive red colour. Grows accompanied by two other alien: left the Australian fern Adiantum hispidulum and right the American Tradescantia fluminensis, the three perfectly adapted to the Azorean climate.

Belongs to the family of Blechnaceae, like the Woodwardia radicans and Blechnum spicant. Its spores are dispersed by wind (anemochory) and, once they have germinated, its prothallus or gametophyte gives rise to a sporophyte or real fern, or by sexual reproduction through fertilization of the female oosphere by a male antherozoids or by apogamy (gametophytic apomixis), growing the sporophyte directly from a somatic cell of the gametophyte bypassing sexual fertilization. It has a short rhizome covered with long light brown scales. Its fronds are dimorphic, the fertile grow upright, stiff and end in a long narrow apex caudate (Latin caudatus caudata, caudatum = with tail), a detail that gives the species name, while the barren, arranged in a basal rosette, are looser and have a pendulum bearing.

Another robust Doodia caudata with upright fertile fronds in early May in the Natural Park of Madeira. To the left is a copy of the fern Anogramma leptophylla. Constant humidity provided by the typical horizontal rain of Macaronesian islands facilitates their survival. (Double click on the photo to enlarge)
It is treated contemptuously as vermin plant, an invasive weed, by become feral very easily and escape from the gardens through the dispersal of spores. She has no guilt. Not voluntarily traveled from the Southern Hemisphere to the Northern Hemisphere, but was brought there by man. Does the same as any other living creature, trying to survive and perpetuate their species on Earth. Evil does not exist in nature, only in the heart of man. The truth is that this is a beautiful fern that grows without forming large populations. Most specimens found in the Azores and Madeira were solitary individuals, not harmed in any other species or competing for territory. In the two photos above and the following is clearly what I mean.

Young specimen surrounded shoots of Tradescantia fluminensis, interspersed with outbreaks of also alien Selaginella kraussiana.

The fertile fronds (the two red) grow very erect, at the beginning of a bright red, which changes to pink and then to green as they mature fronds. Its pinnae are long and narrow and are separated from each other. Can reach 30 cm in length. The sterile fronds (the left) are somewhat shorter,  pinnae are closely spaced and wider than the fertile and the apex is shorter, less caudate.

Frond of Doodia caudata of leathery texture rough touch with finely serrated leaflets, curved spines lined to the tip of the pinnae, hence also called Doodie aspera ssp. caudata. (Double click on the photo to enlarge)

Underside of the apex very long and narrow, caudate, a fertile frond of Doodia caudata with mature sori reach the tip of the tail in early May.

Middle of the previous frond pinnae finely serrated edge, inserted in the rachis with a broad base and sori of slightly more than 1.5 mm each, often confluent and arranged in two rows on each side of midrib of the pinna.

Detail of mature sori of Doodia caudata with indusium slightly raised so sporangia can deliver and disperse spores, which are carried by the wind (anemochory) as far as possible from his mother to conquer new territories. Double clicking on the picture you can see these details, including tiny sporangia hovering below the indusium, which is membranous and lined with small hair.

Sporangium of Doodia caudata seen under a microscope at 400 magnification. (Double click on the photo to enlarge)

And for finish in this microscopic photo spores can be seen with a nice golden brown colour.

Tuesday, January 4, 2011

Pteris vittata absorbed arsenic to protect itself

The affinity for arsenic of fern Pteris vittata seems a contradiction. What explains the extreme toxicity of this metalloid find it beneficial? The answer is very simple: Pteris vittata accumulates arsenic in its fronds as a defense mechanism against predation by herbivores. Exactly the same as the caterpillars eat poisonous plants and accumulate in their tissues the poison to deter predators. Thus, if a herbivore eats the fronds of Pteris, suffering from severe intoxication and, if not die, will remember the rest of his life unpleasant experience and never going to eat again. This affinity for arsenic is shared by other ferns of order Pteridales such as Pteris cretica, Pityrogramma calomelanos, Pteris longifolia, Pteris umbrosa, etc ...

Magnificent specimens of Pteris vittata grown in the Botanical Garden of Soller in Majorca, with long fronds that can reach 130 cm.

This tendency to hyperaccumulate arsenic was discovered accidentally by finding the first specimens of Pteris vittata growing in Florida, specifically on land heavily contaminated by this metalloid. This detail was very appealing to botanists who made analyzing the composition of several fronds and found in them a high concentration of arsenic up to 1000 times higher than what is considered compatible with life, have been found up to 2.3% of Arsenic in tissues of the fronds.

Small feral Pteris vittata growing in a crack in the facade of a house in the city of Horta on Faial Island in the Azores Archipelago. On these islands, this fern allochthonous Atlantic has become a real plague, favored by high humidity throughout the year.

Facade of a house in the city of Horta on Faial Island with several specimens of Pteris vittata. The Azorean are forced to start each year, many ferns growing on the walls of their homes.

 Ferns  from above seen them closer. (Double click on the photo to enlarge)

Numerous studies have attempted to explain the tolerance of Pteridales to arsenic. The most accepted hypothesis is that once absorbed by the roots the fern fronds sends it where it undergoes a process of chelation (chemical neutralization) followed by a sequestration (encapsulation to isolate the cells).

Young feral Pteris vittata growing in a wall in full sun in the city of Tazacorte in the Canary island of La Palma.

 Pteris vittata petioles much shorter than the lamina up to 15 cms. covered with trichomes.

Frond of fern above with their long leathery leaflets of entire margin.

Logically then saw the great possibilities offered by this fern to decontaminate soils with high concentrations of this poison. The results were startling, making back to life almost dead land, where nothing grew before.

Later some scientists thought in the possibility of using it to decontaminate water with high arsenic concentrations. This was done by hydroponic growing without soil, the roots of ferns directly submerged in contaminated water in containers. The results were even better than in the decontamination of soils. A single plant grown hydroponically in a container with 600 ml of contaminated water reduced the concentration of arsenic from 46 to less than 10 micrograms / liter in only three days, continuing decontamination in the following days, although at a slower speed.

Pteris vittata sori arranged in a submarginal line along the edge of pinnae with a subentire pseudoindusium. Sporangia in the sori of the photo are mature about to embark dispersal of spores.

Sporangium of Pteris vittata with the empty bag after dispersing the spores. The ring has numerous cells of vivid fire colour.. (Double click on the photo to enlarge)

And finally the microscopic picture of the beautiful spores with tetrahedral reticulated faces. (Double click on the photo to enlarge)
 Reticulated faces of the spores.

Environmental arsenic pollution is a problem so serious that many methods have been devised both chemicals, which produce highly toxic waste, at times more polluting than arsenic itself as physical, such as nanofiltration, reverse osmosis, ion exchange , electrodialysis, whose high costs are prohibitive for the battered economies of many countries. Bio-Decontamination for the cultivation of Pteris vittata is therefore the best alternative, because of its simplicity, its excellent results in a short time and low cost.